Method and apparatus for heat treating



Aug. 23, 1966 L. B. KIMBROUGH METHOD AND APPARATUS FOR HEAT TREATING 2Sheets-Sheet 1 Filed Dec. 30, 1965 7 6 2 J P M Q F n 5 WV" FAD J'- 4 cA. a 1 wH 6" Q i E w a vTw m ax .M a F 0 mm .m A m INVENTOR Laurence B.Kimbrough WITNESSES Aug. 23, 1966 B. KIMBROUGH METHOD AND APPARATUS FORHEAT TREATING 2 Sheets-Sheet 2 Filed Dec. 30, 1963 Fig.4.

I Ill/III 71/1] Ill/Ill United States Patent 3,268,370 METHOD ANDAPPARATUS FOR HEAT TREATING Laurence B. Kimbrough, Baltimore, Md.,assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., acorporation of Pennsylvania Filed Dec. 30, 1963, Ser. No. 334,260 9Claims. (Cl. 148-16) The present invention .relates to method andapparatus for heat treating, and more particularly to such method andapparatus involving induction heating of .a metal workpiece surfacewhile in exposure to a select fluid environment.

The select fluid environment is chosen according to the result desired,such as prevention of oxide formation, surface cleansing in a reducinggas,.carburization, etc. Techniques for maintaining such environment insurround of the heated workpiece surface have included the localizedflowing of a gas over such surface, and the surrounding of such surfacewith a liquid. As previously practiced, such techniques have sufferedfrom inefficiencies; the migration of air into the flowing gas, in theone case, and use of an excessive amount of induction heating power inevaporation and/ or heating of liquid surrounding the heated workpiecesurface, in the other case.

In view of the foregoing remarks, it becomes an object of the presentinvention to provide an improved method and apparatus for inductioncontrolled-fluid-environment heat treating, which overcomes theabove-mentioned disadvantages of the exemplified previous techniques.

In accord with general features of the present invention, a workpiecesurface is heated by induction heating coil means while a select gas ismaintained in contact with such surface and while a pool of liquid isused as a seal against access of air to such surface.

In accord with a supplanting aspect of the present invention, where animmersion quench is suited to the desired heat treatment, the aforesaidpool of liquid may be made to serve as an immersion quench bath.

Other objects, advantages, and aspects of the invention will be madeapparent in the following detailed description taken in connection withthe accompanying drawings, in which:

FIGURE 1 is an elevation view, substantially in cross section, showing anovel apparatus operable to perform the novel method of the presentinvention; v

FIGURE 2 is a similar view of a modification of the apparatus of FIGURE1;

FIGURE '3 illustrates an apparatus in conjunction with a particularsurface of a workpiece having a configuration which affords its servingas container for the aforementioned pool of liquid, which assemblage isoperable in accord with the novel method of the present invention;

FIGURE 4 is an elevation view, substantially in cross section, showingapparatus of the present invention as applied to horizontal-scanningheat treatment of a workpiece; and

FIGURE 5 is a section view taken along the line 4-4 in FIGURE 1 showinga detail of the heating coil means as exemplified in the apparatus ofFIGURES 1, 2, 3 and 4.

Referring to FIGURE 1 in the drawings, in accord with the illustrativeembodiment shown therein, an elongated workpiece 5, in the form of a rodor shaft, to be heat treated is arranged to extend vertically into apool 6 of liquid,'such as water, for example, disposed in a vessel 7. Aninduction heating coil 8 is disposed in the pool 6 in encirclement of alongitudinal portion of the workpiece, together with a gas housing 9 incontiguous axialwise extension with respect to the heating coil 8.

The vessel 7 for the liquid pool 6 can take the form such assemblage.

pf an open-top cylindrical tank as illustrated in FIGURE l, or otherwiseprovide for the retention of a liquid pool 3,268,370 Patented August 23,1966 "Ice while permitting insertion of a workpiece or/ and of heatingcoil and gas housing, according to convenience and/or requirement. Inthe FIGURE 1 exemplification, the configuration of the workpiece 5 issuch as would permit the induction coil 8 and gas housing 9 assemblageto maintain a fixed position within the vessel 7, inasmuch as theworkpiece 5 may be inserted axialwise into Other workpiececonfigurations might preclude such axialwise insertion and dictate needfor radialwise insertion in a hinged or split form (not shown) of gashousing and heating coil, in which case the act of introducing theworkpiece to such assemblage might better be carried out outside thevessel 7 and then inserted in toto thereinto.

The induction heating coil 8 as exemplified herein is of a single turnconfiguration of the water-cooled integralquench type havingspaced-apart hollow leads 12 at a circumferential location on the coil.These hollow leads 12 serve the usual function of conveying energizingcurrent, cooling water, and quench water to the coil. This particularcoil configuration is particularly suited to the heating of a narrowlongitudinal zone of a cylindrical workpiece, as chosen for exampleherein, and particularly to scanning of the workpiece by such zone byrelative axialwise movement between workpiece and coil, while theworkpiece is rotated for uniform circumferential induction heatingefiect. Where the heat treating requires a rapid quench, as in surfacehardening certain steels, for

example, a forced quench such as a water spray is delivered to theheated workpiece surface via spray ports 16 in the coil during thescansion of the workpiece. In accord with certain features of theinvention, however, the heating coil may be of another configuration,scansion of the workpiece may not be involved, nor liquid quenching beinvolved. Per the illustrative examples shown herein, the split in thecoil 8 in the region of the leads 12 may be filled with an electricalinsulating material 17, FIGURE 5, to prevent flow of liquid from thepool 6 radially therethrough while immersed as in FIGURES 1, 2 and 3.

The gas housing 9 has a liquid-tight connection with the top of theheating coil 8 and extends vertically therefrom in spaced-apartencirclement of the workpiece 5 to a closure portion 19 at its upper endto define a clearanceway 20 which opens downwardly to the interior ofthe coil 8. The housing 9 is adapted for connection to a source of gasunder pressure (not shown) via gas supply conduit means 22 and valvemeans 23, to avail the clearanceway 20 of such gas via an annular headerchamber 24 and ports 25 located at the top of such housing. In the FIG-URE 1 showing, the upper closure portion 19 of the housing 9 comprises asealing ring 27 for sealing contact with the peripheral surface of theworkpiece 5 which is of such length as to extend upwardly beyond thehousing 9. In the FIGURE 3 showing, the workpiece 5 is a short hollowcylindrical part, or hub, of a torque converter housing 30, and theclosure portion 19 takes the form of a Wall which extends over the endof such part. The housing 9 at its area of connection to the heatingcoil 8 and within an area of inductive influence by such coil, is madeof an electrical insulating material such as polypropylene. For sake ofsimplicity, the entire housing may be made of such material, as isindicated in the showing in the drawings. For reasons which hereinafterwill become apparent, the effective clearanceway 20, including thatwithin the coil 8, may be extended downwardly for a distance beneathsuch coil by the inclusion of a cylindrical-gas-housing-extension 32secured in fluid-tight conneciton to such coil.

As aforementioned, one aspect of the invention relates to heating thesurface of the workpiece to a temperature which is conducive of oxideformation when exposed to air and therefore a select fluid environmentis maintained in surround of such surface when in such heated state toprevent such oxide formation. Referring to FIGURE I,

assume that the parts of the apparatus and the workpiece 5 arepositioned as shown, and that the pool 6 of such as water is inexistence within the vessel 7 at least to a height above the bottom ofthe gas-housing extension 32, or of the heating coil 8 if no suchextension is employed. Assume also that the valve 23 is open forconnection of the interior of the gas housing 9 to a source of inertgas, such as argon or nitrogen, for example, and that such interiorpreviously has been purged of air so that only the inert gas is presentin the clearanceway in surround of the outer surface of the workpiecewithin the region of heatability by the induction coil 8. In accord withthe present invention, the liquid of the pool 6, water, for example, inextending to a height above the bottom end of thegas-housing-and-heating-c-oil assemblage 8, 9 acts as a seal whichprevents migration of atmospheric air into clearanceway 20 to theworkpiece surface to be heated. At the same time, once having purgedsuch clearanceway of air, as by displacement with flow of inert gasthereinto, the liquid in surround of the gas-housing-and-heating-coilassemblage 9, 8, in accord with one aspect of the present invention, maybe prevented from entering the interior of such assemblage by merelymaintaining a gas pressure, slightly greater than that created by theliquid of pool 6 extending above the bottom of the assemblage. Actuallythere can be flow of the inert gas under these circumstances, and suchflow serves as further assurance that such gas-present liquid-freecondition persists. An indication thereof may be obtained by thepresence of bubbles 34 rising to the surface of the pool 6. In thehorizontal arrangement of FIGURE 4, such gas flow is necessary, since amere static pressure Will not prevent migration of liquid into the openend of the clearanceway 20.

During the existence of the above-described gas-present liquid-freecondition, the induction heating coil 8 will be energized via leads 12to cause induction heating of a portion of the workpiece 5 disposedtherein. At the same time, per the usual practice in accord with theillustrative configuration of heating coil and workpiece, the workpiecemay be rotated about its axis within the seal 27 of the gas housing 9Without disturbance to the gas-present liquid-free condition inimmediate presence of the heated workpiece surface. Such condition willbe maintained so long as the temperature of such workpiece surfaceremains critically high with respect to oxide formation. Slow cooling ofthe heated workpiece surface may be arrived at by de-energization of theheating coil 8 and such as heat transfer via conduction to the liquidpool 6 and radiation to the liquid-cooled coil. After which cooling, thevalve 23 will be closed and the workpiece, with its heat treated area,removed from the apparatus. Where immersion in a liquid bath quench isdesired for the heated area of the workpiece, as in hardening certainsteel alloys, for example, the liquid of the pool 6 can serve as suchbath by permitting such liquid to rise upwardly through the clearanceway20 to quench the heated workpiece surface. This can readily be arrivedat by operation of the valve means 23 to establish connection of the gashousing 19 to an atmospheric vent port 38 in lieu of the gas supply; itbeing understood that the level of the liquid in pool 6 will need be ata height suificient to cause such rising to the desired height withinthe clearanceway. Where a forced quenching of the heated surface of theworkpiece is required for completion of the desired heat treatment,as'in hardening of certain other steel alloys, a liquid spray of such aswater is directed onto the heated surface via the spray ports 16, forexample, in the exemplified integral-quench heating coil 8.

Where the workpiece 5 is scanned by the heating coil 8 for extension ofthe heated zone along the axis of such workpiece, it will be appreciatedthat the gas housing 9 will follow the movement of the coil to maintainthe heated surface in surround by the select gas and the liquid of thepool 6 will follow such movement to maintain the air-excluding seal forthe gas at the bottom of the moving coil or/and effect progressivequenching of the succeeding portions of the workpiece which becomeexposed to such liquid as the coil moves to simultaneously heat theadvancing preceding surfaces. sion type quench and the forced or sprayquench, the gashousing-extension 32 can serve, where desired, to keepthe liquid-surrounded portion of the workpiece more remote from theportion being heated within the coil 8.

In the exemplified showing in FIGURE 1, it will be apparent thatscanning of the workpiece 5 by a'heated zone can best be effected bymovement of the coil-andgas-housing assemblage 8, 9 while the workpieceremains fixed in position within the vessel 7. Where it may be desirableto instead move the workpiece relative to the coil-and-gas-housingassemblage 8, 9, arrangements such as shown in FIGURES 2 and 4 may beemployed. In the FIGURE 2 arrangement, the vessel 7 may be provided withan opening 40 at its bottom through which the workpiece 5 may extend foraccommodating vertical movement relative thereto and to thecoil-and-gas-housing assemblage 8, 9 therein. A resilient annular seal41 mounted interiorly of the opening 40 provides for retention of theliquid of the pool 6 by slidable sealing cooperation with the exteriorof the workpiece. In the FIGURE 4 arrangement, the workpiece 5 may bemoved horizontally and axialwise through the coil-and-housing assemblage8, 9 via a movable workpiece support means 42a driven by such as ascrew-threaded rotary shaft 4212. In accord with yet another aspect ofthe invention, a liquid such as water is used to effect initialdisplacement of air associated with the workpiece prior to introductionof the select gas, thereby to realize conservation of such gas whichotherwise would need be utilized in excess in order to realize suchdisplacement. Referring to FIG- URE 3, for example, this concept isutilized where the hub portion 5 to be heat treated is of hollowconfiguration. Prior to introduction of the gas housing 9, the bottom ofth hub is closed and sealed by a plug 43 and the interior of such hub isfilled with water. Following this, the encircling annular well of theworkpiece in form of a torque converter housing is filled with water toconstitute the pool 6. The gas-housing-and-coil assemblage 9, 8 is thenlowered onto and around the hub portion to be heat treated. By openingthe top of the gas housing 9 to the atmosphere at this time, as by useof the valve 23, water from. the pool 6 will rise upwardly into theinterior of such housing and effect displacement of the air therein tothe extent permitted by the depth of such pool, thereby further assuringthe purging of the interior of the gas housing of air in order to assuresurround by select gas of the workpiece surface to be heated by the coil8. In the FIGURES 1, 2 and 4 embodiment, an even greater liquid purgingcan be realized. Here, by virtue of the depth of the pool 6, the entireinterior of the gas housing 9 can be filled with the liquid from thepool to displace the .air initially therein. Subsequent to this, theliquid within the housing 9 will then be displaced downwardly byadmittance of the select gas thereinto via valve 23, fluid pressureconduit means 22, and the annular header chamber 24, as previouslydescribed. From the foregoing it will be apparent that there has beendisclosed an improved method and apparatus forcontrolled-fluid-environment heat treating.

While there have been shown and described what are at present consideredto be the preferred exemplifications of the invention, modificationsthereto will readily occur to those skilled in the art. It is notdesired, therefore, that the invention necessarily be limited to thespecific arrangements and steps described and shown, except as areembraced in the appended claims, and it is intended Both in the bathimmer-.

to cover in the appended claims all such modifications as fall withinthe true spirit and scope of the invention.

I claim as my invention:

1. A method of heat treating a workpiece involving heating of a surfaceof such workpiece by induction heating coil means proximate theretowhile such surface is exposed to a select gas environment, comprisingthe establishing of a liquid pool environment in surround of theinduction heating coil means and of the portion of the workpiece havingthe surface to be heated, and causing such select gas to displace theliquid away from said workpiece surface while heating same byenergization of said heating coil means.

2. A method of heat treating a workpiece as set forth in claim 1,wherein the workpiece surface is to be heated and quenched and theliquid of the pool is caused to come into contact with the heatedworkpiece surface for immersion quenching thereof.

3. A method of heat treating a workpiece comprising directing a selectgas onto the surface of such workpiece while heating same inductively,and employing a liquid pool in a manner serving as a seal againstmigration of atmospheric air to the workpiece surface While in itsheated state and in the presence of said select gas.

4. A method of heat treating a workpiece comprising establishing aliquid environment in surround of the surface of the workpiece to beheated, causing a select gas to displace the liquid away from suchsurface, and heating said surface inductively in the presence of saidselect gas while it maintains displacement of the liquid.

5. Apparatus for heating a workpiece surface while in exposure to aselect gas, comprising means defining a pool of liquid for surround ofthe workpiece surface, induction heating coil means disposed in saidliquid in inductive coupling relationship with said workpiece surfacefor heating same, and means for directing a select gas onto saidworkpiece surface in displacement of said liquid while said surface isin a heated state.

6. The heating apparatus of claim 5, further including means foreffecting scanning of said workpiece surface by said heating coil meansand by the select gas directing means.

7. Apparatus for heating a peripheral workpiece surface while inexposure to a select gas, comprising an induction heating coil forencirclement of such surface to inductively heat same, a cylindrical gashousing means for encirclement of said surface and cooperation with saidheating coil to direct a flow of select gas onto the workpiece surfacedisposed within said heating coil, and means for defining a pool ofliquid to seal against migration of atmospheric air onto the heatedworkpiece surface in the presence of said select gas.

8. The apparatus of claim 7, wherein said gas housing means includes amechanical sealing means for cooperation with said workpiece to causesuch select gas flow to be unidirectional.

9. Apparatus for heat treating a workpiece surface, induction heatingcoil means for inductively heating said surface, gas housing means fordirecting a select gas onto such surface while being so heated, andvessel means for containing a pool of liquid extending to a level abovesaid heating coil means and gas housing means.

References Cited by the Examiner UNITED STATES PATENTS 3/1963 Chang14820.3 X 8/1965 Snoue l4820.3

1. A METHOD OF HEAT TREATING A WORKPIECE INVOLVING HEATING OF A SURFACEOF SUCH WORKPIECE BY INDUCTION HEATING COIL MEANS PROXIMATE THERETOWHILE SUCH SURFACE IS EXPOSED TO A SELECT GAS ENVIRONMENT, COMPRISINGTHE WESTABLISHING OF A LIQUID POOL ENVIRNOMENT IN SURROUND OF THEINDUCTION HEATING COIL MEANS AND OF THE PORTION OF THE WORKPIECE HAVINGTHE SURFACE TO BE HEATED, AND CAUSING SUCH SELECT GAS TO DISPLACE THELIQUID AWAY FROM SAID WORKPIECE SURFAE WHILE HEATING SAME BYENERGIZATION OF SAID HEATING COIL MEANS.